Endogenous biological rhythms synchronise human physiology with daily cycles of light-dark, wake-sleep and feeding-fasting. Proper circadian alignment is crucial for physiological function, reflected in the rhythmic expression of molecular clock genes in various tissues, especially in skeletal muscle. Circadian disruption, such as misaligned feeding, dysregulates metabolism and increases the risk of metabolic disorders like type 2 diabetes. Such disturbances are common in critically ill patients, especially those who rely on enteral nutrition. Whilst continuous provision of enteral nutrition is currently the most common practice in critical care, this is largely dictated by convenience rather than evidence. Conversely, some findings indicate that intermittent provision of enteral nutrition aligned with daylight may better support physiological functions and improve clinical/metabolic outcomes. However, there is a critical need for studies of skeletal muscle responses to acutely divergent feeding patterns, in addition to complementary translational research to map tissue-level physiology to whole-body and clinical outcomes.

A person’s chronotype reflects individual variability in diurnal rhythms for preferred timing of sleep and daily activities such as exercise and food intake. The aim of this review is to provide an overview of the evidence around the influence of chronotype on eating behaviour and appetite control, as well as our perspectives and suggestions for future research. Increasing evidence demonstrates that late chronotype is associated with adverse health outcomes. A late chronotype may exacerbate the influence of greater evening energy intake on overweight/obesity risk and curtail weight management efforts. Furthermore, late chronotypes tend to have worse diet quality, with greater intake of fast foods, caffeine and alcohol and lower intake of fruits and vegetables. Late chronotype is also associated with eating behaviour traits that increase the susceptibility to overconsumption such as disinhibition, food cravings and binge eating. Whether an individual’s chronotype influences appetite in response to food intake and exercise is an area of recent interest that has largely been overlooked. Preliminary evidence suggests additive rather than interactive effects of chronotype and meal timing on appetite and food reward, but that hunger may decrease to a greater extent in response to morning exercise in early chronotypes and in response to evening exercise in late chronotypes. More studies examining the interplay between an individual’s chronotype, food intake/exercise timing and sleep are required as this could be of importance to inform personalised dietary and exercise prescriptions to promote better appetite control and weight management outcomes.

Obesity is a chronic, complex and multi-factorial condition with an increasing prevalence worldwide. Irregular eating schedules might be a contributing factor to these numbers through the dysregulation of the circadian system. Time-restricted eating (TRE), an approach that limits eating windows, has been studied as a strategy to treat obesity, aligning eating occasions with metabolic circadian rhythms. This review aims to provide an overview of the impact of TRE protocols on metabolic, inflammatory, oxidative stress and circadian rhythm biomarkers in people with overweight or obesity. Most studies report significant weight loss following TRE protocols. While glucose levels decreased in nearly all TRE interventions, only a few studies demonstrated statistically significant differences when compared to the control groups. The findings for c-reactive protein and TNF-α were inconsistent, with limited significant differences. Changes in lipid profile changes were variable and generally did not reach statistical significance. Both 4-hour and 6-hour TRE interventions significantly reduced 8-isoprostane levels. Additionally, TRE significantly altered clock gene expression, as well as that of genes associated with metabolic regulation in subcutaneous adipose tissue. While the evidence is still inconsistent, limiting eating to a consistent daily window of 8 to 12 h can improve insulin sensitivity, reduce blood glucose, cholesterol and triglyceride levels and promote weight loss. These effects are likely attributable to both direct metabolic impacts and indirect benefits from weight loss and improved dietary habits. However, data on circadian, inflammatory and specific metabolic biomarkers remain scarce and occasionally contradictory, highlighting the need for further research on these interventions.

Sleep is vital for the maintenance of physical and mental health, recovery and performance in athletes. Sleep also has a restorative effect on the immune system and the endocrine system. Sleep must be of adequate duration, timing and quality to promote recovery following training and competition. Inadequate sleep adversely impacts carbohydrate metabolism, appetite, energy intake and protein synthesis affecting recovery from the energy demands of daily living and training/competition related fatigue. Sleep’s role in overall health and well-being has been established. Athletes have high sleep needs and are particularly vulnerable to sleep difficulties due to high training and competition demands, as such the implementation of the potential nutritional interventions to improve sleep duration and quality is commonplace. The use of certain nutrition strategies and supplements has an evidence base i.e. carbohydrate, caffeine, creatine, kiwifruit, magnesium, meal make-up and timing, protein and tart cherry. However, further research involving both foods and supplements is necessary to clarify the interactions between nutrition and the circadian system as there is potential to improve sleep and recovery. Additional research is necessary to clarify guidelines and develop products and protocols for foods and supplements to benefit athlete health, performance and/or recovery. The purpose of this review is to highlight the potential interaction between sleep and nutrition for athletes and how these interactions might benefit sleep and/or recovery.

As obesity rates rise globally, addressing modifiable lifestyle factors, such as sleep, presents an opportunity for public health interventions. This review explores the growing evidence linking sleep duration, quality and timing with weight management and dietary behaviours throughout the life course. Observational studies associate short or irregular sleep with increased obesity risk, poor diet quality and metabolic disturbances. Plausible mechanisms include decreased physical activity, heightened hedonic and/or emotional eating, dysregulated appetite signals and circadian misalignment of metabolism, which contribute to a positive energy balance. Unravelling the bidirectional relationship between sleep and weight is challenging; poor sleep exacerbates weight gain, while obesity-related comorbidities such as obstructive sleep apnoea further impair sleep. Despite promising evidence from sleep-restriction studies showing increased energy intake, long-term randomised controlled trials (RCTs) examining interventions designed to improve sleep with weight management as an outcome are lacking. A handful of short-term interventions suggest benefits in reducing energy intake or improving dietary quality, but their effects on weight loss remain inconclusive. This review calls for robust, well-powered RCTs that integrate sleep, diet and physical activity interventions to evaluate the potential of sleep as a core component of obesity prevention and treatment strategies. Currently, there is insufficient evidence to support sleep-focused interventions as a mandatory element in clinical weight-management programmes.

The potential influence of the timing of eating on body weight regulation in humans has attracted substantial research interest. This review aims to critically evaluate the evidence on timed eating for weight loss, considering energetic and behavioural components of the timing of eating in humans. It has been hypothesised that timed eating interventions may alter energy balance in favour of weight loss by enhancing energy expenditure, specifically the thermic effect of food. This energetic effect has been suggested to explain greater weight loss which has been observed with certain timed eating interventions, despite comparable self-reported energy intakes to control diets. However, timed eating interventions have little impact on total daily energy expenditure, and the apparent effect of time of day on the thermic effect of food largely represents an artefact of measurement methods that fail to account for underlying circadian variation in RMR. Differences in weight loss observed in free-living interventions are more likely explainable by real differences in energy intake, notwithstanding similar self-reported energy intakes. In addition, the energetic focus tends to overlook the role of behavioural factors influencing the timing of eating, such as appetite regulation chronotype-environment interactions, which may influence energy intake under free-living conditions. Overall, there is scant evidence that timed eating interventions are superior to general energy restriction for weight loss in humans. However, the role of behavioural factors in influencing energy intake may be relevant for adherence to energy-restricted diets, and this aspect remains understudied in human intervention trials.

Chrono-medicine considers circadian biology in disease management, including combined lifestyle and medicine interventions. Exercise and nutritional interventions are well-known for their efficacy in managing type 2 diabetes, and metformin remains a widely used pharmacological agent. However, metformin may reduce exercise capacity and interfere with skeletal muscle adaptations, creating barriers to exercise adherence. Research into optimising the timing of exercise has shown promise, particularly for glycaemic management in people with type 2 diabetes. Aligning exercise timing with circadian rhythms and nutritional intake may maximise benefits. Nutritional timing also plays a crucial role in glycaemic control. Recent research suggests that not only what we eat but when we eat significantly impacts glycaemic control, with strategies like time-restricted feeding (TRF) showing promise in reducing caloric intake, improving glycaemic regulation and enhancing overall metabolic health. These findings suggest that meal timing could be an important adjunct to traditional dietary and exercise approaches in managing diabetes and related metabolic disorders. When taking a holistic view of Diabetes management and the diurnal environment, one must also consider the circadian biology of medicines. Metformin has a circadian profile in plasma, and our recent study suggests that morning exercise combined with pre-breakfast metformin intake reduces glycaemia more effectively than post-breakfast intake. In this review, we aim to explore the integration of circadian biology into type 2 diabetes management by examining the timing of exercise, nutrition and medication. In conclusion, chrono-medicine offers a promising, cost-effective strategy for managing type 2 diabetes. Integrating precision timing of exercise, nutrition and medication into treatment plans requires considering the entire diurnal environment, including lifestyle and occupational factors, to develop comprehensive, evidence-based healthcare strategies.

Anaemia affects more than 36 % of all pregnancies globally and is associated with significant maternal and neonatal morbidity and mortality. Iron deficiency is widely recognised as the most common nutritional cause of anaemia but other nutrient deficiencies are also implicated, including the B vitamin riboflavin, albeit its role is largely under-investigated and thus typically overlooked. Riboflavin, in its co-factor forms flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), is required for numerous oxidation-reduction reactions, antioxidant function and in the metabolism of other B vitamins and iron. While clinical deficiency of riboflavin is largely confined to low-income countries, sub-clinical (functional) deficiency is much more widespread, including in high-income countries, and is particularly common among women of reproductive age and during pregnancy. Limited observational evidence from high-income populations suggests that suboptimal riboflavin status contributes to an increased risk of anaemia. Furthermore, randomised controlled trials in pregnant women from low- and middle-income countries have demonstrated beneficial effects of riboflavin on haematological status and anaemia. Various mechanisms have been proposed to explain the contribution of riboflavin deficiency to anaemia, with the strongest evidence pointing to an adverse effect on iron metabolism, given that riboflavin co-factors are required for the release of iron from storage ferritin in the production of red blood cells. Overall, this review investigates riboflavin intakes and status during pregnancy in different populations and evaluates the available evidence for the under-recognised role of riboflavin in the maintenance of haemoglobin concentrations together with its potential to protect against the development of anaemia during pregnancy.

The over consumption of high fat, sugar, and salt foods increases population risk of overweight, obesity and diet-related noncommunicable diseases. The food environment mediates consumer food choices and thus plays an important role in diet quality and related health outcomes. The built food environment, where most people in high-income countries access their food, has been found to be obesogenic. The aim of this review was to investigate the healthfulness of the supermarket food environment. Supermarkets are an important source of healthy foods in the built food environment. However, there are disparities in access to supermarkets, and in several countries, supermarkets located in areas of higher deprivation have an unhealthier consumer food environment. This double burden limits access to healthy foods amongst lower socio-economic groups, contributing to widening disparities in food-related ill health. There is a strong body of evidence supporting improved purchase of healthy foods by increasing the healthfulness of the supermarket consumer food environment. Voluntary measures co-designed with retailers to improve the healthfulness of the supermarket consumer food environment through restriction of product placement and private label reformulation have led to an increase in healthier food purchases. However, evidence also shows that mandatory, structural changes are most effective for improving disparities in the access to healthy food. Future research and policy related to the food environment should consider equitable access to healthy sustainable foods in built and online supermarkets.

In recognition of the impact of current dietary patterns on human and environmental health, dietary shifts towards sustainable diets are considered crucial to adequately feed a growing global population within planetary boundaries. Whilst the composition of sustainable diets varies to account for regional specificity, consensus exists on the need to reduce meat and increase plant protein intakes in sustainable dietary patterns for high-income settings. Due to the high environmental impact resulting from meat production and observational evidence of higher risks of negatives health outcomes associated with excess red and processed meat, a reduction in meat consumption is considered a ‘win-win’ for both people and the planet. However, meat is an important contributor to dietary protein and micronutrient intakes and plays an important sociocultural role, particularly in the UK and Ireland. Whilst a strong evidence-base exists on the environmental and health benefits associated with increased consumption of whole plant foods such as legumes, nuts and seeds, these foods may not address the barriers associated with lower meat diets. Plant-based meat alternatives (PBMAs) are products created to replicate the taste, texture, appearance and functionality of meat and therefore may provide an acceptable means of facilitating the shift to healthy and more sustainable diets. However, less is known about the health and environmental impact of substituting meat with PBMAs. Therefore, this review summarises the literature on the nutritional, health and environmental impact of PBMAs to better understand the role of these products in healthy and sustainable diets for the UK and Ireland.

Gestational diabetes mellitus (GDM) poses significant health concerns for women and their offspring, with implications that extend beyond pregnancy. While GDM often resolves postpartum, a diagnosis of GDM confers a greater risk of future type 2 diabetes (T2D) and other chronic illnesses. Furthermore, the intergenerational impact of GDM predisposes offspring to increased chronic disease risk. Despite the awareness of the short- and long-term consequences of GDM, translating this knowledge into prevention strategies remains challenging. Challenges arise from a lack of clarity among health professionals regarding roles and responsibilities in chronic disease prevention and women’s lack of awareness of the magnitude of associated health risks. These challenges are compounded by changes in the circumstances of new mothers as they adjust to balance the demands of infant and family care with their own needs. Insights into behaviour change strategies, coupled with advances in technology and digital healthcare delivery options, have presented new opportunities for diabetes prevention among women with a history of GDM. Additionally, there is growing recognition of the benefits of adopting an implementation science approach to intervention delivery, which seeks to enhance the effectiveness and scalability of interventions. Effective prevention of T2D following GDM requires a comprehensive person-centred approach that leverages technology, targeted interventions and implementation science methodologies to address the complex needs of this population. Through a multifaceted approach, it is possible to improve the long-term health outcomes of women with prior GDM.